Administrative Privileges: It is important that the Nexus Mod Manager has administrative privileges granted because some components of the application need certain privileges that only an administrator possesses the right to grant.
However, if you want to conserve space in a specific Hard Drive by installing the game on one and the Mods on another the Nexus Mod Manager does allow you to do this but in order to achieve this, you have to enable Multi HD Install during the installation process of the NMM. This can prevent the Nexus Mod Manager from loading the Mods because internet service might be essential for certain Mods. If these files were not configured when Nexus Mod Manager was installed the Mods will not work with the game. ini files inside the data folder of the game have to be properly configured to work with the Nexus Mod Manager and the game.